A variable-size bed which can function as both a sleeping arrangement (larger bed size) and a seating arrangement (smaller bed size) is particularly advantageous in applications such as truck or lorry cabs where the space may be too limited to have both a dedicated sleeping arrangement and a dedicated seating arrangement.
For instance, the patent document GB 1 538 525 discloses a lorry cab in which a back seat comprises a seat cushion and a backrest. The seat cushion can be selectively moved into a forward couch position and a rearward seat position. In the seat position, the cushion is adjacent to a rear wall of the cab, providing leg space between the cushion and the back of a driver's seat in front of the back seat for comfortable seating. In the couch position, the cushion is at a greater distance from the cab's rear wall, which distance is bridged over by a tensioned support made in one piece with a top covering of the cushion. The support may be rolled up.
However, a problem with the solution in GB1 538 525 is that the seat cushion itself provides the same comfort both in the couch and seat positions, whereas it usually is more preferable to have softer comfort in a sleeping arrangement and harder comfort in a seating arrangement. Further, in the couch position, the complete bed area or bed face where a person should lie and sleep is only partly supported by the underlying seat cushion (while the remaining area is “supported” by the tensioned support). Therefore, the support for the person lying on the bed area may be uneven, which could make the arrangement uncomfortable to rest on.